Raspberry Pi Media Center is a series of Raspberry Pi Zero-based media center devices. They share a similar look, and compared to my earlier designs, they have a great-looking aluminum case.
- Raspberry Pi Media Center
I did few audio projects in the past, some using ESP32, some using larger Orange Pi and Raspberry Pi devices. Each has its pros and cons, and with each iteration, I'm trying to focus on the details that were working best for me, while actually using them.
What is special about the Raspberry eco-system is of course its community support. Being a not-so-strong software developer, I often have to rely on the work that other people did and baked into the base Raspbian image. Attaching a DAC, Ethernet, and IR reader is as simple as adding 3 lines into the config.txt file
dtoverlay=gpio-ir,gpio_pin=23
dtoverlay=w5500
dtoverlay=hifiberry-dac
All the device tree definitions, kernel drivers, and dependency packages are already in place, believe it or not.
Sure, compared to the ESP32 platform it is not as lightweight. It requires more power, it takes some time to boot. But when it comes to rapid development, there is nothing like the Raspberry Pi.
Raspberry Pi HiFi is a first-in-line product that uses the legendary PCM5100 series DAC with supreme audio quality. It exposes line-level output that you can plug into a stereo amplifier. Spend as much as you need on the external amp to deliver the sound you like (personally I prefer late 80's audio gear).
Loud Raspberry Pi uses a dual MAX98357 HiFi DAC with a built-in highly efficient D-class amp to deliver 3 to 5W of music power directly to your speakers. It is not too loud, but also very simple to use and fun to play with. It powers from a standard USB-C power source, like a phone charger, etc.
Louder Raspberry Pi is a top-of-the-range model that uses a modern highly capable TAS5805M DAC and is aimed to be paired with medium-to-large speaker systems. With 25W per channel stereo output, it packs a punch and can easily enliven living quarters or dorm rooms. It is highly efficient, but much more demanding for power when cranked, therefore it uses USB-C Power Delivery to pull up to 65W from the wall power adapter. It can be used both with Wi-Fi and Ethernet (to make sure bad Wi-Fi would not interrupt the stream)
| HiFi Raspberry | Loud Raspberry | Louder Raspberry | |
|---|---|---|---|
| Image |  |
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| DAC | PCM5100A 32bit Stereo DAC | Dual I2S DAC MAX98357 with built in D-Class amp | Stereo I2S DAC TAS5805M with built in D-Class amp |
| Output | 2.1 VRMS Line level output -100 dB typical noise level |
2x 3W (8Ω); 2x 5W (4Ω) | 2x 22W (8Ω, 1% THD+N); 2x 32W (4Ω, 1% THD+N) |
| RGB LED | yes | yes | yes |
| External relay driver | yes | no | yes |
| Ethernet | Wiznet W5500 SPI Ethernet | Wiznet W5500 SPI Ethernet | Wiznet W5500 SPI Ethernet |
| Powers from | 5V USB-C power adapter (up to 1 A) Triple LP5907 3.3 V Ultra-Low-Noise LDO |
5V USB-C power adapter (up to 3 A) | 65W USB-C PD power adapter (25W/45W with limited power) |
| Mechanical dimensions (WxHxD) | 88mm x 38mm x 100mm | 88mm x 38mm x 100mm | 88mm x 38mm x 100mm |
| I2S CLK | I2S DATA | I2S WS | MAX98357A EN (Loud only) | |
|---|---|---|---|---|
| Raspberry Pi Zero (BCM) | 18 | 21 | 19 | 4 |
| SPI CLK | SPI MOSI | SPI MISO | LAN RES | LAN CS | LAN INT | WS2812 RGB LED | RELAY EN | IR INPUT | |
|---|---|---|---|---|---|---|---|---|---|
| Raspberry Pi Zero (BCM) | 11 | 10 | 9 | 24 | 8 | 25 | 12 | 7 | 23 |
| I2C CLK | I2C DATA | DAC PWDN | DAC FAULT | PD POWER GOOD | |
|---|---|---|---|---|---|
| Raspberry Pi Zero (BCM) | 3 | 2 | 4 | 26 | 16 |
Being a Raspberry Pi software selection is a vast space for experimentation. First things first, for any OS you need to configure DAC. Then we talk about different OS options.
You can use any distribution you like. The only change you need to make to enable hardware is to add 3 lines to the /boot/config.txt
dtoverlay=gpio-ir,gpio_pin=23
dtoverlay=w5500
dtoverlay=hifiberry-dac
As simple as HiFi model, just add 3 lines to the /boot/config.txt
dtoverlay=gpio-ir,gpio_pin=23
dtoverlay=w5500
dtoverlay=max98357a-overlay
TAS5805M DAC is not supported by default Raspbian distribution, therefore some work needs to be done to enable it. Linked repo contains code and instruction on how to configure it. It will take you 5 minutes and one reboot.
With the bare OS you're in full control of what to install and configure. IT is totally up to your use case.
| Raspbian | DietPi | PostmarketOS | |
|---|---|---|---|
| Link | link | link | link |
| Code | link | link | link |
| Based on | Debian | Debian | Alpine |
| Type | Bare OS | Base OS | Bare OS |
This is a work in progress and the idea is to have a bare minimum OS (be it Raspbian, DietPi, or Armbian) and install the most used client services via the Ansible playbook. I will add more details, as soon as I have working samples, but planned things to add are
- Spotify Connect
- Apple Airplay
- Mpd
- Network Pulsesink
- UPNP sink
- Snapcast client
- Slimproto client
- Basic UI with configuration
This will allow to integrate into existing media sources with Home Assistant, LMS, or Mopidy instance, including multi-room sync.
| HifiBerry OS | PiCorePlayer | MupiBox | Mopidy | Volumio | Moode | Balena Audio | |
|---|---|---|---|---|---|---|---|
| Link | link | link | link | link | link | link | link |
| Code | link | link | link | link | link | link | link |
| Based on | Debian | Tiny Core Linux | DietPi | Debian | Debian | Debian | Balena |
| Type | OS + Services | OS + Services | OS + Services | Services only | OS + Services | OS + Services | OS + Services |
| Remote management | No | No | No | No | No | No | Yes |
| SW support | |||||||
| UI/UX features | |||||||
| Web UI | Yes | Yes | Yes | Yes | Yes | Yes | |
| Mobile App/UI | Yes | Yes | Yes | Yes | Yes | ||
| IR Remote | ? | Yes | ? | ? | ? | ? | Custom |
| Server features | |||||||
| LMS server | Yes | ? | No | ? | ? | ? | |
| Local library | Yes | Yes | Yes | Yes | Yes | ||
| Radio providers | Yes | Yes | Yes | Yes | Yes | ||
| Snapcast server | ? | ? | ? | ? | ? | ? | Yes |
| Client features | |||||||
| LMS Client/Squeezelite | Yes | Yes | ? | No | Yes | Yes | ? |
| Airplay | Yes | Yes | ? | No | Yes | Yes | Yes |
| Spotify | Yes | Yes | Yes | No | Yes | Yes | Yes |
| Snapcast client (HA) | Yes | ? | ? | ? | ? | ? | Yes |
| Pulseaudio sink | ? | ? | ? | ? | ? | ? | Yes |
| UPNP/DLNA client | Yes | Yes | Yes | ||||
| MPD | Yes |
Volumio is a great piece of software, extremely popular with media center devices like Raspberry Media Center. With HiFi Raspberry and Loud Raspberry, things are fairly simple. Those DACs are supported out of the box. Select HiFiBerry DAC and Adafruit MAX98357 in the DAC Model settings accordingly. Optionally you may also create a /boot/userconfig.txt file and add the following config to enable W5500 Ethernet
[all]
dtoverlay=w5500
For Louder Raspberry, you'd need to perform a few more steps to configure a custom DAC.
First, get access to the terminal either from USB-Serial or from SSH. To enter the Serial terminal you'd need to add this line to /boot/volumioconfig.txt
enable_uart=1
You can enable SSH at volumio.local/dev and log in using user volumio and password volumio
Assuming you're in, first install build prerequisites (this will take a while, grab a coffee)
volumio kernelsource
Next, pull the DAC driver from the GitHub
cd ~
git clone https://github.com/sonocotta/tas5805m-for-raspbian-paspberry-pi-zero
cd tas5805m-for-raspbian-paspberry-pi-zero
Build kernel driver
cd /usr/src/rpi-linux && sudo find . -type d -exec chmod 755 {} \; # no idea why permissions are not right, but this should fix it
make all
If all goes well you should see no errors in the console
make -C /lib/modules/6.1.77+/build M=/home/volumio/dev/tas5805m-for-raspbian-paspberry-pi-zero modules
make[1]: Entering directory '/usr/src/rpi-linux'
CC [M] /home/volumio/dev/tas5805m-for-raspbian-paspberry-pi-zero/tas5805m.o
MODPOST /home/volumio/dev/tas5805m-for-raspbian-paspberry-pi-zero/Module.symvers
CC [M] /home/volumio/dev/tas5805m-for-raspbian-paspberry-pi-zero/tas5805m.mod.o
LD [M] /home/volumio/dev/tas5805m-for-raspbian-paspberry-pi-zero/tas5805m.ko
make[1]: Leaving directory '/usr/src/rpi-linux'
Copy over kernel drivers to filesystem
sudo make install
Now let's compile and copy device tree
sudo apt install device-tree-compiler -y
sudo ./compile-overlay.sh
Next, we need to update the Volumio settings. Navigate to /volumio/app/plugins/system_controller/i2s_dacs/dacs.json file and add this line as the first choice in the Raspberry PI section
{"id":"louder-raspberry","name":"Louder Raspberry","overlay":"tas5805m,i2creg=0x2d","alsanum":"2","alsacard":"LouderRaspberry","mixer":"Master","modules":"tas5805m","script":"","needsreboot":"yes"},
Restart the Volumio service
sudo systemctl restart volumio.service
Now you should be able to select Louder Raspberry in the DAC list, which will restart the Raspberry
At this stage it is not changing DT overlay automatically, I need to figure out why, but for now let's add it manually to the end of the /boot/config.txt file
#### Volumio i2s setting below: do not alter ####
dtoverlay=tas5805m,i2creg=0x2d
After reboot, you should be able to see new sound card via aplay -l
card 2: LouderRaspberry [Louder-Raspberry], device 0: bcm2835-i2s-tas5805m-amplifier tas5805m-amplifier-0 [bcm2835-i2s-tas5805m-amplifier tas5805m-amplifier-0] ^F Forward
Subdevices: 1/1
Subdevice #0: subdevice #0
Volumio will start playing using the right DAC on its own. Congratulations!
On some systems W5500 driver will rotatre the chip's MAC address on each boot, which is quite annoying if you're binding DHCP server to them. There is a manual fix that can help with that
- Downloaded the w5500 overlay file
- uncomment this line and change the MAC to your liking // local-mac-address = [aa bb cc dd ee ff];
- save the file as w5500-overlay-custom.dts
- create the binary with the following command:
dtc -I dts -O dtb -o w5500-custom.dtbo w5500-overlay-custom.dts - backup the original w5500.dtbo:
sudo mv /boot/overlays/w5500.dtbo /boot/overlays/w5500.dtboBACKUP - move the new .dtbo into the overlays directory:
sudo cp w5500-custom.dtbo /boot/overlays/w5500.dtbo - reboot and ip a will report the new MAC address
Please visit the hardware section for board schematics and PCB designs. Note that PCBs are shared as multi-layer PDFs as well as Gerber archives.
| Front | Back | PCB |
|---|---|---|
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| Front | Back | PCB |
|---|---|---|
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| Front | Back | PCB |
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According to the manufacturer Raspberry Pi Zero requires at least 1 Amp of 5V line, and each of the Loud Raspberry DAC needs at least 1 Amp extra. With the total budget requirement of 3 Amps, it is within specs for a non-PD USB-C 5V power line. I've decided not to use USB-PD for The Loud model. Just make sure your power adapter is capable of 3 Amps (or keep a reasonable volume if it is not).
HiFi Raspberry barely uses extra power compared to what the Raspberry Pi Zero board itself needs. No special requirements are there.
For Louder Raspberry, it is clearly not an option. You'd need a PD-enabled power adapter to run the board. Ideally, you should supply a 20V 3.25 Amp capable power source, common for modern laptops (Dell, HP, and Lenovo all tested and work perfectly). However, pretty much any 9V/12V/20V PD-enabled power adapter will work, most typically phone chargers with a quick charge option. The smallest of the family is a 25W model, which is plenty enough for both Raspberry Pi and DAC.
The interesting part was all the phone and laptop chargers I used for the test (around five different makes of each), sounded great, with no hissing, no popping. (Apart from the Apple ones, they didn’t work. Likely they have Apple-specific PD protocol). This is probably because modern devices have become so noise-sensitive that manufacturers have been forced to do good work on noise levels.
Tested and perfectly working models are (others may be available)
| Model | Image |
|---|---|
| 65W USB-C Lenovo ThinkPad Laptop Charger Replacement Power Adapter |  |
| 65W 45W 20V 3.25A Type-C PD Laptop Charger |  |
| 120W Gan Type-C PD Charger |  |
| 45W Type-C PD Mobile Phone Wall Adapter |  |
One caveat is that, since Raspberry Pi requires 5V to run and the input voltage is in the range of 5 to 20 volts, I failed to find a step-down converter that (a) supports this wide input range and (b) can run in no-dropout mode (meaning keep 5V output on 5V input). If you know one, please let me know. But at this moment you have to supply more than 5V over USB (meaning 9V in PD standards) to start the Raspberry.
Now, you have USB power delivery and the Serial on the same bus, how should this work then? When you're developing, you may not require the full power of the DAC, and it will happily work with 5V input (limited to something like 5W of music power per channel). you just supply 5V to the Raspberry using a micro-USB cable, while USB-C will power the DAC with 5V and give you a Serial console at the same time
HiFi version of the Raspberry Media Center has an internal driver for the external relay. It has a back-facing diode to shunt any coil-inducted currents. Driver is an open-drain output with the following states
| Driver Pin State (IO7) | Output state | Relay connected between OUT and +5V |
|---|---|---|
| Floating (pulled low with 100K resistor) or LOW |
High impedance | INACTIVE (switched OFF) |
| HIGH | Pulled to GND | ACTIVE (switched ON) |
Schematics:
External relay can be connected directly between OUT and +5V pins (1st and 3rd pins, mid pin being GND)
Start by configuring IR device-tree overlay in the /boot/config.txt file
# Enable IR reader on GPIO23
dtoverlay=gpio-ir,gpio_pin=23
After reboot, you should be able to see /dev/lirc0 device
$ ls -al /dev/lirc0
crw-rw---- 1 root video 251, 0 Jun 17 21:51 /dev/lirc0
There are multiple ways you can capture IR signals using /dev/lirc0 device, one of them is to use lirc utilities by installing them via
$ sudo apt install lirc -y
Next we need to pull the remote configuration or create new one by training lirc. First path is much easier, you may find your remote in the library here. Pull it into lirc config by running
$ cd /etc/lirc/lircd.conf.d/
$ sudo wget -O aa59-00741a.lircd.conf https://sourceforge.net/p/lirc-remotes/code/ci/master/tree/remotes/samsung/aa59-00741a.lircd.conf?format=raw
$ sudo service lircd restart
To be sure, I've updated also /etc/lirc/lirc_options.conf changing 2 lines
driver = default
device = /dev/lirc0
Next capture incoming IR codes by running
$ irw
00000000e0e0e01f 00 KEY_VOLUMEUP Samsung_TV
00000000e0e0e01f 01 KEY_VOLUMEUP Samsung_TV
00000000e0e0e01f 00 KEY_VOLUMEUP Samsung_TV
00000000e0e0d02f 00 KEY_VOLUMEDOWN Samsung_TV
00000000e0e0d02f 01 KEY_VOLUMEDOWN Samsung_TV
The tested method of controlling RGB LED is to use rpi_ws281x library, available as rpi-ws281x-python module. You can install it with pip. This library uses PWN capabilities of the GPIO and does not require any specific device tree configuration. The only configuration that you'd need in any of the provided examples is below
# LED strip configuration:
LED_COUNT = 1
LED_PIN = 12
LED_FREQ_HZ = 800000
LED_DMA = 10
LED_BRIGHTNESS = 255
LED_INVERT = False
LED_CHANNEL = 0
Unfortunately, this library uses direct access to memory, so you need to run it as root.
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